Electric-resistance thermometer.



No. 845,413. PATENTED FEB. 26, 1907. E. HAAGN. ELECTRIC RESISTANCE THERMOMETER.

APPLICATION FILED SEPT. 22. 1906.

WW 66 gm} 5 M UNITED STATES PATENT OFFICE.

ERNST HAAGN, OF HANAU, GERMANY, ASSIGNOR TO THE FIRM OF W. C. HERAEUS, OF HANAU, GERMANY.

Specification of Letters Patent.

Patented Feb. 26, 1907.

Aymlication filed September 22,1906. Serial No. 835,825.

To all whom it may concern:

Be it known that I, ERNST HAAGN, a subject of the German Emperor, and a resident of Hanau, Germany, have invented certain new and useful Improvements in Electric- Resistance Thermometers, of which the following is a specification.

This invention relates to electrical-resistance thermometers by which the well-known property of a wire to alter its resistance by a change of temperature is used for thermometrical purposes. Several measuring instruments which are based on this principle are on the market. Commonly platinum wire is used for this pur ose, because platinum is less altered while eing incandescent. This platinum wire is commonly wound on a reflecting-strip if low temperatures are to be dealt with, and if high temperatures are to be dealt with it is wound on a clay cylinder, and these windings are embedded into an isolating protecting receptacle. This construction is unsatisfactory to some extent, because the platinum wire is not arranged in intimate contact with the wall of the outer receptacle, and in consequence the heat to be measured must first cross an air-space, which is a bad heat-conductor, and therefore prevents a quick reaction of the instrument. A further disadvantage is that when hi her temperatures are to be dealt with the p atinum undergoes an, although slight, atomization and oxidation, which is followed by a more or less great alteration of the resistance.

The present invention has the purpose of overcoming these difficulties and to provide an instrument which reacts quickly up to 1,000 centigrade, and in consequence permits a relative accuracy up to 1/1000 even at high temperatures.

The instrument arranged according to my said invention is as follows, reference being had to the accompanying drawings, in which- Figure 1 is a view of the instrument before the rod and wire are embedded into the outer tube, and Fig. 2 a view of the instrument ready for use after embedding.

The platinum wire a, the resistance of which is employed for measurin the temperature, is Wound spirally aroun a quartzglass rod b, when a thin uartz-glass tube 0 1s drawn over the rod an wire and melted or fused onto the'same insuch a way that no intermediate space is left between them; but the rod b and the tube 0 are melted or fused together in one piece, completely embedding the wire in the glass. This is effected in the following manner: The narrow tube c,drawn over the rod b, is evacuated and then softened by heatin it to 1,500 centigrade, when it lays [itself tightly'on the rod b and both melt tothey are heated considerably at a much lower electrical charge, so that faults of measuring are unavoidable. The platinum wire being in its whole length intimately embedded in the quartz-glass it transfers its whole own heat perfectly to the quartz-glass body, so that a heating of the wire is avoided.

In the drawings, d are the ends of the platinum wire, which ends lead to the terminals of the source of electricity and to the measuring instrument.

I claim 1. The method substantially as hereinbefore described of making an electric-resistance thermometer, which consists in winding a platinum wire spirally on a quartz-glass rod, drawing over the latter a quartz-glass cylinder, and intimately uniting the cylinder-rod and wire by fusing the cylinder and rod together.

2. The method substantially as hereinbefore set forth of making an electric-resistance thermometer, which consists in winding a platinum wire spirally on a quartz-glass rod, drawing over the latter a quartz-glass tube evacuatin the tube, and fusing the tube an rpd toget er, embedding the wire in the ass.

g 3. As a new article of manufacture an electric -resistance thermometer, consisting name to this specification in the presence of of a quartz-glass fodha plzzitinum wire wound two subscribing witnesses. spirally over saic r0 an an outer uartzglass layer, the rod and layer being fu sed to- ERNST HAAGN' gether completely embedding the wire in the Witnesses: glass. JEAN GRUND,

In testimony whereof I have signed my 1 CARL GRUND. 

